2015 Yuletide Lecture: Climate Change

2015 Yuletide Complexity Lecture

Climate Change: Sorting the facts from the hype – Dr Ed Hawkins


On Monday 14th December the Nonlinear and Complex Physics Group held it’s annual Yuletide Lecture at IoP HQ in London. Dr Ed Hawkins from the National Centre for Atmospheric Science at the University of Reading delivered a fascinating and very well-attended talk on Climate Change: Sorting the facts from the hype. The topic of climate change was particularly poignant as the 21st Conference of Parties summit in Paris had just reached its conclusion, with political leaders from around the world managing to reach an agreement on a set of targets to tackle climate change. Dr Hawkins had spent a few days as an observer at the meeting so was able to give some insights into the process, as well as provide an overview of the scientific evidence that underpins the need for such an agreement. He began by highlighting some key points, putting the political negotiations in Paris into the context of the scientific evidence: 1) The response to tackling climate change should be based on the best scientific evidence, 2) Limiting global temperature increases requires a balance between sources of emissions (such as greenhouse gases) and sinks (absorbers of carbon), 3) COP21 led to an agreement between 195 nations who aim to limit global temperature rise to well below 2 degrees, and to pursue efforts to limit global warming to 1.5 degrees.

Dr Hawkins led us through some of the history of climate science, showing that our understanding of climate change is routed in fundamental physics and chemistry of the 19th Century. Joseph Fourier made the first calculations of the Earth’s energy balance using arguments about the incoming and reflected energy from the sun. By this argument alone he calculated that the planet should be much colder than what was observed. John Tyndall carried out experiments in 1861 that demonstrated the greenhouse effect in the lab. This allowed Guy Callendar to connect the missing heat from Fourier’s calculations to the natural greenhouse gases present in the atmosphere and led him to the first predictions of global temperature rise from increasing CO2 from human influence.

Dr Hawkins also examined some of the multiple lines of evidence that gives scientists a deeper understanding of climate variability and change. These include observations over the recent past to understand where signals of climate change are already emerging from variability, sophisticated climate models to perform ‘what if’ experiments, attributing causes of change and predict what might happen in future, as well as examining longer historical (paleoclimate) records, which show that we are currently experiencing atmospheric greenhouse gas levels and global temperatures that are much higher than we have seen for hundreds of thousands of years.


Finally, Dr Hawkins highlighted that while climate scientists are sure about the reality of human made climate change, there are aspects of the details that are less certain. If decisions about how to tackle climate change are to be based on the scientific evidence then, he argued, scientists need to be clear about what we are confident about and what we are less confident about. As for the decisions themselves; well those are left to the politicians.

Report by Emma Suckling